Method and Apparatus For Separating Liquid Droplets From a Gas Stream

ABSTRACT

A method and apparatus for separating liquid droplets from a gas stream. The method includes the steps of conditioning the gas stream which contains the droplets so that the gas stream exhibits substantially turbulent flow, passing the gas stream generally axially through a flowpath so that the gas stream is in communication with a collector surface, collecting the droplets on the collector surface, and draining the collector surface to remove the collected droplets from the collector surface. The apparatus includes a flowpath, a collector surface for collecting the droplets, a flow conditioner for conditioning the gas stream, and a drainage mechanism for draining the collected droplets from the collector surface.

FIELD OF THE INVENTION

A method and apparatus for separating liquid droplets from a gas stream.

BACKGROUND OF THE INVENTION

Separation of very fine liquid droplets from a gas is required in manyapplications where finely dispersed liquid droplets are used in chemicalor energy processes.

One example involves the fine pulverization of water prior to admissioninto the suction side of a compressor, aiming at increasing theeffectiveness of a (turbo) compressor by cooling the gas beforeadmission. Even if it is assumed that cooling-evaporation consumes70-80% of the liquid dispersed into atomized droplets, approximately 20%of the liquid in the form of fine droplets remain and enter thecombustion chamber (of the gas turbine power equipment). Due to theresulting “humid” nature of the combustion gas, the system efficiency,while considerably increased by cooling the air prior to compression,may be reduced by 2% or more. In the case of a 10 MW gas turbine unitsuch a reduction in efficiency represents a significant amount of energy(which is consumed as latent heat for evaporation in the combustionchamber).

In a second example, a fine pulverization is required to increase thecontact area of a liquid reactant in order to improve the contact areain a chemical reaction (e.g., 1 liter=1 dm³ of liquid pulverized to a 5μm droplet size will acquire an exchange area of approximately 4800 m²).

In a third example, aiming at the removal of extremely fine solidparticles, a particle cloud is “chased” by pulverized liquid dropletswhich are formed by a pulverization process. A correlation is requiredbetween the size distribution of the solid particles and the sizedistribution of the liquid droplets (which “chase” and coalesce with the“dust-like” solid particles) in the range of “a similar order ofmagnitude” (e.g. micron for micron).

In a fourth example a gas may be selectively separated using anon-contact (surface) gas extraction device. Atomization of a fine cloudof a selective adsorbent/absorbent in the form of a dense cloud ofmicro-droplets will represent a solution which will avoid the need forfilm or solid support surfaces.

In a fifth example, liquid micro-droplets may result from a process ofbulk condensation, where a humid gas (containing water or any othersolvent in a gaseous form) is exposed to a pressure-temperature processand with the aid of a large population of sub-“micronic” impurities(usually present in any industrial gas) offers conditions for “bulkcondensation” of the liquid micro-droplets.

In a sixth example, a number of technologies can be grouped together inthe field of “direct contact heat & mass exchangers” which may be usedto avoid the use of conventional bulky equipment, fouling, corrosion,large capital & operation costs and to take full advantage of existingor created micro-droplets of liquid for contacting gas or solids (infine particulate form) and/or for the enhancement of chemical reactions,evaporation processes, heat transfer processes and mass transferprocesses.

Although the technology of atomizing or pulverizing liquids intodroplets is well represented in the technical literature (see forexample “Atomization & Sprays”, A. H. Lefebre, printed by Taylor &Francis-Hemisphere, 1989), the next important stage of almost any suchmodern processing system, consisting of the effective separation of the“processed” or created micro-droplet population (usually suspended by agas), is not well developed, is difficult and represents the maindeterrent for a broader application of direct-contact technologies(micro-droplets of liquid direct contacting gas and/or dust-likemicro-particles).

In any separation technology a proper balance between separationefficiency, maintenance cost and minimization of pressure drop, whetherin a clean or clogged state, is essential. Some exemplary separationtechnologies disclosed in the art include the following:

-   -   (a) particles to be separated are electrically charged prior to        entering the separator apparatus and meet walls carrying an        opposite electrical charge (electrostatic or AC/DC). Aqueous        droplets are generally avoided due to high-electrical        conductance and other electrically related safety concerns, with        the result that electrically based separation technologies        typically cannot be used for separating aqueous or highly        electrically conductive liquids. These technologies do, however,        provide a “wall extraction” but in a laminar, quiescent flow        regime, which detracts from the system efficiency but enhances        the particle removal mechanism;    -   (b) filters and coalescers, metallic and non-metallic pads and        micro-porous filled containers for liquid droplets and solid        particles may represent viable alternatives for some        applications. These technologies can be used in tailored        applications but require frequent maintenance, particularly        where impurities are attached to any of the phases of the fluid        system being treated. Clogging is one of the more important        problems associated with these types of separation technologies.        Where “plugging” impurities are attached to one or more phases        of the fluid system being treated, and where large amounts of        gas throughput should be processed with minimum pressure drop,        the use of micro-porous container or pads system is typically        excluded, thus eliminating the application of these types of        technologies from fluid systems carrying “gum-like” suspensions        (as in oil/gas fields), which have the tendency to rapidly        deteriorate the flow-pressure drop characteristics of the fluid        flow and render the technology inefficient or unacceptable;    -   (c) mechanical separation technologies may be used to separate        liquid droplets from some fluid systems, but the separation of        liquid micro-droplets entrained by a gas is known to pose        practical problems with most conventional mechanical separator        designs including gravitational separators which depend upon        gravity settling and according to Stokes' Law require a        residence time (Liquid Volume (m³)/Throughput in (m³/h)) in        excess of the time required for a liquid particle to reach the        liquid-gas interface. For example, for a liquid micro-droplet        having a size of 5 μm (1 μm=1 m/10⁶), a free falling velocity in        air is obtained (from Stokes' Law) according to Equation 1:

$\begin{matrix}{U_{droplet} = {{\frac{d_{p}^{2}\left( {\rho_{liq} - \rho_{air}} \right)}{18\eta}g} = {{{\frac{\left( {{5/10^{6}}m} \right)^{2}\left( {1000 - 1} \right)\left( {k\; g\text{/}m^{3}} \right)}{{18\left\lbrack {\left( {0.02{cP}} \right)/1000} \right\rbrack}\left( {{kg}\text{/}{ms}} \right)}9.81\left( {m\text{/}s^{2}} \right)} \approx {0.06\text{/}100\left( {m\text{/}s} \right)}} = {0.6{mm}\text{/}s}}}} & (1)\end{matrix}$

-   -    where U_(droplet) is the free falling velocity, dp is the        spherical diameter of droplet/particle (falling under Stokes'        Law), μ is the viscosity in SI units (1 cP=1/1000 kg/m s), and ρ        is the densities of water (for the water droplets) and gas.    -    For a gas space of 0.5 m, a 5 μm droplet will require        approximately 1000 s (16 minutes) to reach the liquid level, for        a 2 μm micro-droplet, the required time (in absolutely still        air) is more than 30 min.    -    Conventional (gravity/cyclone) separation are customarily        designed for a “free gas” velocity of approximately 0.1-0.3 m/s.        At this order of velocity magnitude, all droplets having a        free-falling velocity an order of magnitude smaller will        typically be entrained and will not fall and separate.        Therefore, any technology using a “gravity separation mechanism”        is not typically feasible for the separation of liquid        micro-droplets from gas streams.    -   (d) cyclone, rotational, and other inertial separation        technologies may also be used to separate liquid droplets in        some applications. In these technologies, the effect of        separation may be intensified using a “cyclone” or other        inertial effect. This may be visualized if, in Equation (1) the        acceleration due to gravity (g=9.81 m/s²) is replaced by        centrifugal acceleration Rω² (m/s²). Measured as a “multiple of        “g”, centrifugal acceleration is practically limited to about        5-10 times “g” (or a maximum of 40 g for extremely expensive        separation units and about 100 g for special “multiple plate        designs”). Even if a “10 g” separation apparatus is utilized,        the centrifugal acceleration achieved may not be high enough for        effective separation of micro-particles.    -    A self-generated (swirl flow) cyclone will typically achieve        relatively low “g” values unless extremely high pressure drops        are acceptable in the system. Another solution would be to        create a “compact” unit where the “free falling distance to        interface” is significantly reduced (to be in the order of about        1 centimeter) in order to reduce the required residence time for        separation. This approach is used for some special (heavy oil)        liquid-liquid-solid separators, where the viscosity of the        continuous phase (i.e., the carrier) is a deterrent to the use        of other technologies.

SUMMARY OF THE INVENTION

The present invention includes a method and apparatus for separatingliquid droplets from a gas stream. The liquid droplets may be comprisedsolely of liquid or the liquid droplets may contain solid particlesand/or entrained gas.

The liquid droplets may be comprised of any liquid or combination ofliquids, the solid particles contained in the liquid droplets (wherepresent) may be comprised of any solid or combination of solids, theentrained gas contained in the liquid droplets (where present) may becomprised of any gas or combination of gases, and the gas stream may becomprised of any gas or combination of gases.

Preferably, the invention is used generally for removing impurities fromthe gas stream, where “impurities” may include any unwanted liquid orsolid. The removal of such impurities may be desirable in order toprotect equipment which is to be exposed to the gas stream from foulingor malfunctioning as a result of the presence of the impurities, or toincrease the efficiency of such equipment.

In preferred embodiments, the invention is intended for use in removingliquid droplets substantially comprising water (with or without solidparticles) from a gas stream which may for example be comprised of airor hydrocarbon gas. In a particular preferred embodiment, the inventionis intended for use in removing liquid droplets such as water dropletsfrom natural gas fuels in order to protect burner systems in coldclimates from clogging and malfunctioning due to the formation of icedeposits.

The invention may in principle be used to remove liquid droplets of anysize from a gas stream, but is considered to be most beneficial for usein separating droplets having a size within a range of sizes of betweenabout 1 μm and about 100 μm, between about 1 μm and about 50 μm or evenbetween about 1 μm and about 20 μm, since droplets within these sizeranges are typically very difficult to separate using either gravity orinertial separation technologies.

As a result, allowing for droplet size distributions within a gasstream, preferably at least fifty percent by weight of the liquiddroplets have a size within the size ranges identified above.

Embodiments of the invention are based upon some or all of the followingprinciples:

-   -   (a) liquid droplets entrained in a gas stream will be attracted        by interfacial tension or adhesion forces to a collector surface        such as a collector wall;    -   (b) the likelihood or probability of liquid droplets moving        close enough to the collector surface for the adhesion forces to        collect the droplets on the collector surface as collected        droplets can be significantly enhanced by exposing the gas        stream to the collector surface under substantially turbulent        flow conditions, such that the droplets are directed to randomly        contact (or nearly contact) the collector surface; and    -   (c) coalescing of the collected droplets on the collector        surface can produce a population of coalesced collected droplets        which can subsequently be separated from a gas phase using        gravitational or inertial separation technologies.

In a first apparatus aspect, the invention is an apparatus forseparating liquid droplets from a gas stream, comprising:

-   -   (a) a collector surface for collecting the droplets as collected        droplets; and    -   (b) a drainage mechanism associated with the collector surface        for removing the collected droplets from the collector surface.

In a second apparatus aspect, the invention is an apparatus for removingliquid droplets from a gas stream, the apparatus comprising:

-   -   (a) a flowpath for the gas stream, the flowpath comprising a        flowpath inlet;    -   (b) a collector surface, positioned adjacent to the flowpath so        that the gas stream is in communication with the collector        surface as the gas stream passes through the flowpath, for        collecting the droplets as collected droplets;    -   (c) a flow conditioner in communication with the flowpath inlet,        for conditioning the gas stream to provide substantially        turbulent and generally axial flow of the gas stream through the        flowpath; and    -   (d) a drainage mechanism associated with the collector surface,        for draining the collected droplets from the collector surface.

In a third apparatus aspect, the invention is an apparatus for removingliquid droplets from a gas stream, the apparatus comprising:

-   -   (a) a plurality of parallel flowpath assemblies, each of the        flowpath assemblies comprising:        -   (i) a flowpath for the gas stream, the flowpath comprising a            flowpath inlet;        -   (ii) a collector surface, positioned adjacent to the            flowpath so that the gas stream is in communication with the            collector surface as the gas stream passes through the            flowpath, for collecting the droplets as collected droplets;        -   (iii) a flow conditioner in communication with the flowpath            inlet, for conditioning the gas stream to provide            substantially turbulent and generally axial flow of the gas            stream through the flowpath;        -   (iv) a drainage mechanism associated with the collector            surface, for draining the collected droplets from the            collector surface; and    -   (b) a distributor associated with the flowpath inlets, for        distributing the gas stream to the flowpaths.

In a first method aspect, the invention is a process for separatingliquid droplets from a gas stream, comprising:

-   -   (a) providing a collector surface;    -   (b) exposing the gas stream to the collector surface under        substantially turbulent flow conditions in order to cause the        droplets to accumulate on the collector surface as collected        droplets; and    -   (c) removing the collected droplets from the collector surface.

In a second method aspect, the invention is a method of removing liquiddroplets from a gas stream, comprising:

-   -   (a) conditioning the gas stream so that the gas stream exhibits        substantially turbulent flow;    -   (b) passing the gas stream generally axially through a flowpath        under substantially turbulent flow conditions so that the gas        stream is in communication with a collector surface positioned        adjacent to the flowpath, thereby causing the droplets to        collect on the collector surface as collected droplets; and    -   (c) draining the collector surface to remove the collected        droplets from the collector surface.

The collected droplets are preferably permitted or encouraged tocoalesce on the collector surface before the collected droplets aredrained from the collector surface, so that the collected droplets formsmall pools, liquid films or rivulets of coalesced collected droplets onthe collector surface. Such coalesced collected droplets are relativelyeasy to drain from the collector surface and may themselves function toattract and collect additional droplets or solid particles on thecollector surface. In addition, such coalesced collected droplets, oncedrained from the collector surface, are relatively more easy to separatefrom a gas phase using gravitational or inertial separation technologiesthan are the liquid droplets before they are collected and coalesced.

An important feature of the invention is that substantially turbulentflow in the gas stream in the vicinity of the collector surface isprovided. In other words, the flow of the gas stream through theflowpath should at least exhibit a Reynolds number which exceeds theminimum Reynolds number for transition from laminar flow to turbulentflow so that the flow can be considered to be either transitional orfully turbulent. More preferably, the flow of the gas stream through theflowpath should exhibit a Reynolds number which is near to or exceedsthe minimum Reynolds number for fully turbulent flow so that the flowcan be considered to be fully turbulent.

As a result, the term “turbulent flow” as used herein is intended toencompass flow which may be considered to be either transitional orfully turbulent, but which preferably is fully turbulent. The term“substantially turbulent flow” as used herein is intended to encompassturbulent flow in which minor or insubstantial portions of the gasstream may not experience turbulent flow at a particular time orlocation.

The scale dimension “L” and superficial gas velocity “U” shouldtherefore most preferably be designed so that the Reynolds number (Re)equals or exceeds the critical Reynolds number (Re_(cr)) for fullyturbulent flow with a particular configuration of flowpath and collectorsurface, so that Re≧Re_(cr) where:

$\begin{matrix}{{Re} = {\frac{{U\left( {m\text{/}s} \right)} \times {L\left( {{{geometry}\mspace{14mu} {factor}} - m} \right)}}{v\left( {m^{2}\text{/}s} \right)}( - )}} & (2)\end{matrix}$

where U is the average gas stream velocity in m/s, L is a geometryfactor (for pipes L=inside diameter (m)), and υ is the gas kinematicviscosity in (m²/s). As an example, for a gas absolute viscosity of 0.02cP and a density of 1.2 kg/m³ , the gas kinematic viscosity is: υ(m²/s)=0.02 cP/(1.2 kg/m³/1000)=16.6 (m²/s).

A preferred goal of the invention is to minimize re-atomization andre-entrainment back into the gas stream of collected droplets which havecollected and coalesced on the collector surface (resulting from thecollection of the droplets on the collector surface and subsequentcoalescence of the collected droplets). An alternate preferred goal ofthe invention is to provide that if droplets do become re-atomized orre-entrained in the gas stream, the re-entrained or re-atomized dropletshave a size which is significantly larger than the size of the liquiddroplets which were contained in the gas stream before they werecollected on the collector surface. Preferably the re-atomized orre-entrained droplets have an average size which is at least ten timesthe average size of the original liquid droplets.

It has been found that these goals can be achieved by controlling one ormore flow parameters relating to the flow of the gas stream through theflowpath. Such flow parameters may relate to a maximum Weber numberwithin the flowpath, to the maintenance of annular flow conditionswithin the flowpath, to the superficial gas velocity of the gas streamthrough the flowpath, or to some other parameter.

As a first example, it has been found that by limiting the Weber numberpertaining to the flow of the gas stream through the flowpath to a Webernumber which does not exceed the “film breaking threshold” for thecollected droplets, re-entrainment and re-atomization of collecteddroplets can be minimized. In particular, it has been found that asuitable limit on the value of the Weber number for collected dropletscomprising water is about 30, such that:

$\begin{matrix}{{We} = {{\frac{\rho_{G}U_{G}^{2}d}{\sigma}( - )} \leq 30}} & (3)\end{matrix}$

where We is Weber number, ρ_(G) is the density of the gas phase of thegas stream, U_(G) is the superficial gas velocity of the gas stream, dis the diameter of the droplet and σ is the interfacial tension of theliquid comprising the droplet.

As a second example, it has been found that by limiting the superficialvelocity of the gas stream through the flowpath to a velocity which isless than a “critical atomization gas velocity” of the gas streamthrough the flowpath, the extent of re-atomization and re-entrainment ofthe droplets back into the gas stream can be minimized.

The “critical atomization gas velocity” may be estimated, using anassumed annular flow pattern through the flowpath, as the velocity atwhich a typical droplet formed through breaking and atomization of aliquid film of coalesced collected droplets at the liquid-gas interfacein an annular flow pattern will remain in suspension in the gas stream,according, for example, to the following equations:

$\begin{matrix}{\frac{C_{d}\frac{\pi \; d^{2}}{4}\rho_{G}U_{G}^{2}}{2} = {\frac{\pi \; d^{3}}{6}g\; {\Delta\rho}}} & (4)\end{matrix}$

where C_(d) is the friction coefficient of the droplet, d is thediameter of the droplet, ρ_(G) is the density of the gas phase of thegas stream, U_(G) is the superficial gas velocity of the gas stream, gis acceleration due to gravity, and Δρ is the difference in densitiesbetween the liquid comprising the droplet and the gas phase of the gasstream.

$\begin{matrix}{U_{G} = \left\lbrack \frac{4g\; {\Delta\rho}\; d}{3\rho_{G}C_{d}} \right\rbrack^{1/2}} & (5)\end{matrix}$

where U_(G) is the superficial gas velocity of the gas stream, g isacceleration due to gravity, Δρ is the difference in densities betweenthe liquid comprising the droplet and the gas phase of the gas stream,ρ_(G) is the density of the gas phase of the gas stream, and C_(d) isthe friction coefficient of the droplet.

$\begin{matrix}{{We} = {\frac{\rho_{G}U_{G}^{2}d}{\sigma}( - )}} & (6)\end{matrix}$

where We is Weber number, ρ_(u) is the density of the gas phase of thegas stream, U_(G) is the superficial gas velocity of the gas stream, dis the diameter of the droplet and a is the interfacial tension of theliquid comprising the droplet.

The size of the typical droplet can be estimated by assuming a criticalWeber number for atomization (for example We=30) and by assuming atypical drag coefficient for gas at a high Reynolds number (for exampleC_(d)=0.44), so that by combining Equation (5) and Equation (6), thefollowing equation is obtained:

$\begin{matrix}{U_{{G\; \min}\Rightarrow A}^{S} = {3.1\frac{\left( {\sigma \; g\; {\Delta\rho}} \right)^{1/4}}{\rho_{G}^{1/2}}\left( {m\text{/}s} \right)}} & (7)\end{matrix}$

where U^(S) _(Gmin→A) is the critical atomization gas velocity.

As an example, for a water-air system at a standard temperature of about15 degrees Celsius and a standard pressure of about 1 atmosphere, thecritical atomization gas velocity is about 14.5 meters per second.

At velocities less than the critical atomization gas velocity, dropletsmay break from the liquid film and atomize into the gas stream, but willtend to re-collect on the collector surface (which for the numericalexample above is considered to be a liquid film comprising coalescedcollected droplets, which liquid film has formed on the collectorsurface).

At velocities at or slightly greater than the critical atomization gasvelocity, droplets may become re-atomized or re-entrained in the gasstream, but their size will tend to be significantly larger than thesize of the liquid droplets which were originally contained in the gasstream, thus making the re-atomized and re-entrained droplets relativelymore easy to separate from the gas stream using gravitational orinertial separation technologies.

The use of a moderate but effective substantially turbulent flow in thevicinity of the collector surface in the manner as described abovefacilitates the separation of the droplets from the gas stream at arelatively small pressure drop while preferably maintaining the overallseparation efficiency at desirable levels (for example, above about90%).

The collector surface may be comprised of any surface or combination ofsurfaces which is suitable for collecting the droplets. For example, thecollector surface may be generally planar, may be generally cylindricalor tubular, may be generally rectangular, or may be any other shape orconfiguration. The collector surface may be constructed of metal,non-metal or composite materials. The collector surface may be rigid orflexible and may be stationary or moving. In some embodiments, thecollector surface may be comprised of a liquid surface, which liquidsurface may be supported by a solid surface. The liquid surface may becomprised of a liquid having the same composition as the droplets to becollected, or the liquid surface may be comprised of a liquid having adifferent composition from the droplets to be collected.

The collector surface may be relatively smooth or textured. Preferablythe collector surface is textured. The collector surface may be texturedin any manner, such as by being relatively rough, corrugated, ribbed orwavy, in order to promote turbulent flow of the gas stream past thecollector surface and/or to enhance the collection of the droplets onthe collector surface. The collector surface may also be comprised ofone or more grooves, channels or depressions for collecting the dropletswhich approach the collector surface.

The collector surface preferably is “wettable” by the droplets which areintended to be collected by the collector surface so that the formationof a film of coalesced collected droplets on the collector surface andmovement of the film along the collector surface will be promoted. Inother words, preferably a significant adhesion force will be exhibitedbetween the collector surface and the droplets.

The collector surface may be constructed entirely of a wettable materialor the collector surface may be lined or coated with a wettablematerial. The wettable material is preferably comprised of a solid butmay be comprised of a liquid. For example, the collector surface may becomprised of a solid surface which is lined or coated with a liquidmaterial. The liquid material may be comprised of a liquid having thesame composition as the droplets to be collected, or the liquid materialmay be comprised of a liquid having a different composition from thedroplets to be collected.

The selection of a suitable wettable material will depend upon thedroplets which are intended to be collected by the collector surface.For example, in some applications, it may be desirable for the collectorsurface to be “water-wettable” while in other applications, it may bedesirable for the collector surface to be “oil-wettable”.

The flowpath may be comprised of any pathway for the gas stream whichwill permit communication between the gas stream and the collectorsurface as the gas stream passes through the flowpath. The flowpath maybe surrounded by the collector surface so that the flowpath is definedby the collector surface. Alternatively, the collector surface may bepositioned within the flowpath or positioned adjacent to the flowpath.

In one preferred embodiment, the flowpath is defined by the collectorsurface, which collector surface is comprised of a plurality ofgenerally planar surfaces which together form a generally rectangularconduit for the gas stream. In this embodiment, further collectorsurface area may be provided by inserting within the rectangular conduitone or more additional surfaces such as planar surfaces.

In a second preferred embodiment, the flowpath is defined by thecollector surface, which collector surface is comprised of a generallycylindrical surface such as a pipe which forms a conduit for the gasstream. In this embodiment, further collector surface area may beprovided by inserting within the pipe one or more suitable projectingsurfaces.

The flowpath comprises a flowpath inlet. The flowpath may furthercomprise a flowpath outlet so that the gas stream passes through theflowpath from the flowpath inlet to the flowpath outlet and exits ordrains from the flowpath via the flowpath outlet.

Preferably, however, the flowpath is comprised of a flowpath inlet and aflowpath end so that the gas stream passes through the flowpath betweenthe flowpath inlet and the flowpath end, but does not exit or drain fromthe flowpath via the flowpath end. Instead, the gas stream passesthrough the flowpath and exits the flowpath via a gas drainage mechanismpositioned between the flowpath inlet and the flowpath end.

In some embodiments, the gas stream may drain from the flowpath fromboth a flowpath outlet and from a gas drainage mechanism.

The gas drainage mechanism and the drainage mechanism for the collecteddroplets may be comprised of separate drainage mechanisms or may becomprised of a single combined drainage mechanism for both the collecteddroplets and the gas stream. Preferably the gas drainage mechanism andthe drainage mechanism for the collected particles are comprised of asingle combined drainage mechanism.

The flowpath may be oriented in any direction relative to gravity. Forexample, the flowpath may be oriented so that it is generallyhorizontal, generally inclined or generally declined from the flowpathinlet. Preferably, the flowpath is oriented to be generally declinedfrom the flowpath inlet such that the flowpath outlet or the flowpathend is positioned below the flowpath inlet, in order that the passage ofthe gas stream through the flowpath will tend to encourage the collecteddroplets to move downward relative to gravity, thus promotingcoalescence of the collected droplets and enhancing subsequent drainageof the coalesced collected droplets.

In some embodiments, different portions of the flowpath may be orientedto be generally declined, generally inclined, and/or generallyhorizontal.

The flowpath may be comprised of any cross-sectional shape orcross-sectional area. Where the flowpath is generally cylindrical, thediameter of the flowpath is preferably between about 15 millimeters andabout 50 millimeters. It has been found during modeling of the inventionwith respect to a generally cylindrical flowpath that the ability of thecollector surface to collect droplets diminishes if the flowpath has adiameter smaller than about 15 millimeters or larger than about 50millimeters. Where the flowpath is not generally cylindrical, theoptimum size of the flowpath may be determined through testing or bymodeling.

The flow conditioner may be comprised of any structure, device orapparatus which is capable of conditioning the gas stream to providesubstantially turbulent and generally axial flow of the gas streamthrough the flowpath. Turbulent flow of the gas stream increases theprobability that the droplets will contact the collector surface or beplaced within suitable proximity to the collector surface so that theadhesion forces between the droplets and the collector surface willcause the droplets to become collected on the collector surface.

The generally axial flow of the gas stream distinguishes the inventionfrom inertial separation technologies which utilize cyclonic flow tocause droplets to collect on a surface due to the effects of centrifugalacceleration.

Where the gas stream is not otherwise flowing, the flow conditioner maybe further comprised of a structure, device or apparatus which iscapable of imparting flow to the gas stream. In such circumstances, theflow conditioner may be comprised of a single structure, device orapparatus for performing both of these functions or may be comprised ofa plurality of structures, devices or apparatus for performing thesefunctions.

In some preferred embodiments, the flow conditioner is comprised of anadmission chamber which has a conical shape for progressively increasingthe gas velocity to a level which will provide substantially turbulentflow through the flowpath, having regard to pressure, pressure droplimitations, concentration of droplets in the gas stream, erosioncontrol within the apparatus and other factors. In some preferredembodiments, the flow conditioner may be further comprised of a grid orscreen for achieving pseudo-homogeneous turbulent flow conditions byreducing or eliminating large turbulent vortexes (i.e.,macro-turbulence) resulting from ducts, elbows etc. upstream of the flowconditioner.

In other preferred embodiments the flow conditioner may be comprised ofan orifice which will provide substantially turbulent flow through theflowpath.

Finally, in preferred embodiments, the flow conditioner may be furthercomprised of a pump, a fan or other structure, device or apparatus forimparting flow to the gas stream, in circumstances where the gas streamis not otherwise flowing.

The drainage mechanism may be comprised of any structure, device,apparatus or system for draining the collected droplets from thecollector surface. For example, the drainage mechanism may be comprisedof a vacuum system or a mechanical wiper system for removing thedroplets from the collector surface.

Preferably the drainage mechanism is further comprised of the gasdrainage mechanism for draining the gas stream from the flowpath.

Preferably the drainage mechanism is comprised of one or more aperturesdefined by the collector surface. More preferably the drainage mechanismis comprised of one or more slits defined by the collector surface. Inpreferred embodiments the drainage mechanism is comprised of a pluralityof slits which are spaced axially along the collector surface betweenthe flowpath inlet and the flowpath outlet. The slits preferablyfunction both to drain the collected particles from the collectorsurface and to drain all or a portion of the gas stream from theflowpath.

The slits are preferably defined by the collector surface so that theyare oriented transverse to the flowpath.

The slits are preferably sized and spaced along the flowpath to providefor an adequate slit area to drain effectively the collected droplets.In embodiments where all or a portion of the gas stream is to be drainedfrom the flowpath via the slits, the slits are preferably sized andspaced to provide for an adequate slit area to drain effectively boththe collected droplets and the gas stream. In such embodiments, theslits are also preferably sized and spaced to provide a relativelyuniform and limited superficial gas velocity through each of the slitsand to provide a relatively low pressure drop as the gas stream drainsthrough the slits.

For example, the slits may be spaced and sized so that there isrelatively more slit area toward the flowpath inlet and relatively lessslit area toward the flowpath outlet or flowpath end. This result can beachieved by decreasing the frequency and/or size of the slits from theflowpath inlet toward the flowpath outlet or flowpath end. The slits mayalso be spaced and sized so that the total slit area is approximatelyequal to the cross-sectional area of the flowpath, so that thesuperficial gas velocity of the gas stream through the slits is slightlyless than or approximately equal to the superficial gas velocity of thegas stream through the flowpath. Preferably the superficial gas velocityof the gas stream through the slits is slightly less than thesuperficial gas velocity of the gas stream through the flowpath.

The drainage mechanism may be further comprised of textures or shapesformed in the collector surface. For example, the collector surface maydefine troughs or grooves for collecting the droplets or coalescing thecollected droplets and directing them toward the apertures for removalfrom the collector surface. Preferably the collector surface isconfigured so that the collected droplets are allowed to move along thecollector surface toward the apertures under the influence of gravity.In preferred embodiments this result may be achieved by inclining ordeclining the flowpath.

The apparatus may be further comprised of a collection vessel associatedwith the drainage mechanism for receiving and/or storing the collecteddroplets or coalesced collected droplets which are drained from thecollector surface. The collection vessel may also function to receiveand/or store the gas stream which has been drained from the flowpath viathe drainage mechanism.

Preferably the drainage mechanism communicates with a single collectionvessel. Alternatively, a plurality of collection vessels may beprovided. The collection vessel may be open or closed, but is preferablyclosed so that one or more gas phases can be received and stored in thecollection vessel.

The collection vessel may function only to receive and/or store thedrained collected droplets and the drained gas stream. Alternatively,the collection vessel may comprise a secondary separation vessel forseparating constituents of the drained collected droplets and thedrained gas stream into a plurality of products. The secondaryseparation occurring in the collection vessel may utilize gravitationalor other separation techniques. The products obtained from the secondaryseparation may be disposed of, returned to the overall process, orrecovered for other uses.

The collection vessel may be positioned at any location relative to theflowpath and the collector surface. For example, the collection vesselmay be positioned so that it is remote from the flowpath and thecollector surface and even in a separate building or installationtherefrom. In some preferred embodiments, the collection vessel maysubstantially or completely surround the flowpath and the collectorsurface so that the flowpath and the collector surface are fully orpartially contained within the collection vessel.

The apparatus may be further comprised of a cooler associated with theflowpath inlet for cooling the gas stream before it enters the flowpath.The cooler may be comprised of any structure, device or apparatuscapable of removing heat from gases and vapors. Cooling of the gasstream may assist in increasing the efficiency of the apparatus bycondensing vapor or by condensing liquid droplets contained in the gasstream to form larger droplets which are more easily separated. Whereincluded, the cooler is positioned upstream of the flowpath inlet sothat the gas stream can be cooled before it enters the flowpath.Preferably the cooler is positioned before or at the flow conditioner.

The apparatus may be further comprised of a washer for washing orrinsing the collector surface to remove solid residues or impuritieswhich may interfere with the operation of the apparatus. The washer maybe comprised of any structure, device or apparatus which is capable ofremoving such residues and/or impurities. Where provided, the washer ispreferably operated intermittently during times when the gas stream isnot being passed through the flowpath so that the operation of thewasher does not interfere with the operation of the apparatus.

In preferred embodiments, the apparatus may be comprised of a pluralityof flowpaths configured in parallel. The use of a plurality of flowpathsfacilitates an increase in the throughput of the apparatus, potentiallyreduces the overall pressure drop through the apparatus, and may alsoserve to provide a greater surface area of collector surface forcollection of droplets.

The plurality of flowpaths may be isolated from each other orcommunication between the plurality of flowpaths may be provided. Forexample, the plurality of flowpaths may be defined by one or moreaxially extending collector surfaces in the form of walls or dividerswithin a larger flowpath chamber, which walls or dividers may extendcompletely within the flowpath chamber to define isolated flowpaths ormay extend only partially within the flowpath chamber as longitudinalbaffles to define flowpaths which are in communication with each other.

Where the apparatus includes a plurality of flowpaths, the apparatusalso includes a plurality of collector surfaces for collecting dropletsfrom each of the flowpaths. Where the apparatus includes a plurality offlowpaths, the apparatus preferably also includes a distributorassociated with the flowpath inlets for distributing the gas streamamongst the flowpaths.

The distributor may be comprised of any structure, device or apparatuswhich is effective to distribute the gas stream from a source of the gasstream to the plurality of flowpaths. Preferably the distributordistributes the gas stream substantially evenly or such that similarflow conditions are experienced in each of the flowpaths. Thedistributor may be combined with the flow conditioner in a singlecombined apparatus or the distributor may be separate from the flowconditioner.

In preferred embodiments, the distributor is comprised of a manifoldwhich is associated with the flow conditioner such that a singlestructure, device or apparatus performs the conditioning function andthe distributing function.

In some preferred embodiments, the flow conditioner and the distributorare together comprised of an admission chamber and/or grid of the typedescribed for use as the flow conditioner, so that the admission chamberand/or grid communicate with each of the flowpaths.

In some preferred embodiments, the flow conditioner and the distributorare comprised of a distributor manifold comprising turbulence promotingorifices, which distributor manifold both distributes the gas streamamongst the flowpaths and adjusts the velocity of the portion of the gasstream which is delivered to each of the flowpaths.

The method of the invention may be performed using the apparatus of theinvention or may be performed using a different apparatus or combinationof apparatus. Preferably the method of the invention is performed usingthe apparatus of the invention. The method may be performed using asingle flowpath or a plurality of flowpaths.

In the method of the invention, the gas stream conditioning step may becomprised of any procedure or combination of procedures which results inthe gas stream exhibiting substantially turbulent and generally axialflow through the flowpath or flowpaths. In preferred embodiments, thegas stream conditioning step is performed using a flow conditioner ofthe type described for the apparatus of the invention.

In the method of the invention, the gas stream passing step may becomprised of any procedure or combination of procedures which results inthe gas stream communicating with a collector surface positionedadjacent to the flowpath or flowpaths. In preferred embodiments, the gasstream passing step is performed by passing the gas stream through theflowpath or flowpaths from the flowpath inlets to the flowpath outlets.

The gas stream is preferably passed through the flowpath such thatre-entrainment into the gas stream of the droplets which have collectedon the collector surface is minimized. This result may be achieved bycontrolling the flow of the gas stream through the flowpath withreference to one or more flow parameters which are relevant to thepropensity of the droplets to become re-entrained in the gas stream.

According to a first flow parameter, the superficial gas velocity of thegas stream through the flowpath may be maintained at a velocity which isless than the critical atomization gas velocity of the gas stream.According to a second flow parameter, the gas stream may be passedthrough the flowpath under conditions such that the Weber number is lessthan or equal to about 30 (assuming that the collected droplets arecomprised of water). According to a third flow parameter, where theflowpath is generally cylindrical the gas stream may be passed throughthe flowpath substantially under annular flow conditions.

According to a fourth flow parameter, the superficial gas velocity ofthe gas stream through the flowpath or flowpaths may be maintained at nogreater than a maximum value which is dependent upon the composition,temperature and pressure of the gas stream. For example, for a water-airsystem at a standard temperature of about 15 degrees Celsius and astandard pressure of 1 atmosphere, the superficial gas velocity of thegas stream through the flowpath may be maintained at no greater thanabout 10 meters per second, or more preferably at no greater than about8 meters per second, or even more preferably at between about 6 metersper second and about 8 meters per second.

Alternatively, the superficial gas velocity of the gas stream may beslightly greater than is suggested by the above parameters, in whichcase the average size of any droplets which become re-atomized orre-entrained in the gas stream will tend to be significantly larger thanthe average size of the original liquid droplets, and will tend to beseparable from the gas stream using gravitational or inertial separationtechnologies.

In the method of the invention, the collector surface draining step maybe comprised of any procedure or combination of procedures which iseffective to drain the collected droplets from the collector surface orsurfaces.

In preferred embodiments, the collector surface draining step isperformed using a drainage mechanism of the type described for theapparatus of the invention. The draining step may be comprised ofdraining the droplets from the collector surface and draining an amountof the gas stream from the flowpath. In the draining step, all of thecollected droplets may be drained or only a portion of the collecteddroplets may be drained.

Where the draining step is comprised of draining an amount of the gasstream from the flowpath with the collected droplets, the gas stream ispreferably drained so that the superficial gas velocity of the gasstream while being drained is maintained at no greater than a maximumvalue which is dependent upon the composition, temperature and pressureof the gas stream, in order to minimize re-atomization andre-entrainment of the collected droplets as they are being drained, oralternatively in order to maximize the size of any re-atomized orre-entrained droplets.

For example, for a water-air system at a standard temperature of about15 degrees Celsius and a standard pressure of 1 atmosphere, thesuperficial gas velocity of the gas stream while being drained may bemaintained at no greater than about 10 meters per second, or morepreferably at no greater than about 8 meters per second, or even morepreferably at between about 6 meters per second and about 8 meters persecond. Preferably the superficial gas velocity of the gas stream whilebeing drained is slightly less than the superficial gas velocity of thegas stream through the flowpath.

In the method of the invention, the invention may be further comprisedof the step of receiving in a collection vessel the collected dropletswhich are drained from the collector surface or surfaces. The collectionvessel receiving step may be comprised of any procedure or combinationof procedures which is effective to receive the drained droplets. Inpreferred embodiments, the collection vessel receiving step is performedusing a collection vessel of the type described for the apparatus of theinvention. The collection vessel receiving step may be comprised of thestep of receiving in a collection vessel the drained collected dropletsfrom the collector surface or surfaces and the drained gas stream fromthe flowpath or flowpaths.

In the method of the invention, the invention may be further comprisedof the step of separating the drained collected droplets and the drainedgas stream to produce a plurality of products. The separating step maybe performed in any manner, including by using gravitational andinertial separation technologies.

In the method of the invention, the invention may be further comprisedof the step of cooling the gas stream. The gas stream cooling step maybe comprised of any procedure or combination of procedures which iseffective to cool the gas stream. In preferred embodiments, the gasstream cooling step is performed using a cooler of the type describedfor the apparatus of the invention.

In the method of the invention, the invention may be further comprisedof the step of coalescing the collected droplets on the collectorsurfaces before draining the collected droplets as coalesced collecteddroplets. The coalescing step may result in the formation of smallpools, liquid films or rivulets of coalesced collected droplets.

The invention is intended for use in both “clean” and impurities-ladenenvironments. A liquid film comprising collected liquid droplets mayinclude a large portion of solid particles which may be transferred tothe collection vessel, thus minimizing plugging and/or contamination ofthe collector surface and the associated drainage mechanism.

The system of the invention may be used for extraction of solidparticles which are combined with liquid droplets (such as when a mistof liquid is introduced on purpose to absorb or adsorb such solidparticles) or may be used for separation of liquid droplets of thenature obtained during a bulk condensation process.

To take full advantage of a broad spectrum of applications includingchemical reactions, extraction of dust, extraction of any small solidparticles, or removal of liquid micro-droplets, the present invention isdirected at a family of solutions and designs based on “collectorsurface turbulent impact and extraction of droplets and particles” froma gas stream.

In certain applications, the invention may be further comprised of anautomated swing control system for eliminating the collected liquiddroplets from the collector surface at desired levels or time intervals,and/or an automated swing system for executing “on line” washingoperations of one apparatus while a pair apparatus is in operation.

Preferably the apparatus of the invention is designed to minimize thepressure drop experienced by the gas stream as it passes through theapparatus and preferably the method of the invention is performed so asto minimize the pressure drop experienced by the gas stream duringperformance of the method.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to theaccompanying drawings, in which:

FIG. 1A is an elevation longitudinal section drawing of an apparatusaccording to a first preferred embodiment of the invention, utilizing aplurality of planar surfaces as a collector surface.

FIG. 1B is a partial cutaway pictorial drawing of the apparatus depictedin FIG. 1A.

FIG. 2A is an elevation longitudinal section drawing of an apparatusaccording to a second preferred embodiment of the invention, utilizing acylindrical surface or conduit as a collector surface.

FIG. 2B is a transverse section drawing of the apparatus depicted inFIG. 2A, taken along line B-B.

FIG. 2C is a plan longitudinal section drawing of a combinedconditioner/distributor from the apparatus depicted in FIG. 2A, takenalong line C-C.

DETAILED DESCRIPTION OF THE INVENTION

A process involving passage of a gas stream containing droplets mayinclude one or more steps such that a population of liquid droplets (inthe range of, but not limited to between about 1 μm and about 100 μm)has been generated in a previous chemical or thermal process or simplyas a result of condensing, and must be extracted from the carrying gasstream at high efficiency.

The present invention may be used as a stand-alone apparatus or methodor, due to its high efficiency and relatively low pressure dropattributes may be a component of a process involving one or acombination of:

-   -   (a) a preliminary generation of liquid droplets; and    -   (b) a particle liquid/solid contact process or/and a combination        of direct-contact extraction processes where liquid droplets are        involved and must be effectively separated from the carrying gas        stream.

When the invention is used in connection with any prior extractiontechnology requiring a liquid particle final separation the inventionmay therefore be a component of a complete separation process involving:(a) pulverization of the liquid into the liquid droplets (existingtechnology), (b) a direct-contact reaction/extraction using liquiddroplets as an essential contact media, and (c) the use of the inventionfor the separation and/or recovery of the liquid droplets from thecarrying gas stream.

An apparatus or method utilizing the invention includes the followingelements:

(a) Collector Surface

The collector surface is preferably designed for maximum gasstream-surface contact, for drainage and removal of collected dropletsand/or coalesced collected droplets and for minimizing the collectedparticle re-atomization and re-entrainment as a result of high-gasvelocity breaking the film-gas interface. Preferably the collectorsurface functions to enhance collection of the droplets on the collectorsurface, to minimize re-atomization and re-entrainment of the collecteddroplets once they have been collected on the collector surface, topromote the coalescence of collected droplets into small pools, liquidfilms and/or rivulets, and to facilitate the draining of the coalescedcollected droplets such that the droplet size of the coalesced collecteddroplets is significantly larger than the liquid droplets initiallycarried by the gas stream.

The collector surface may be designed as a metallic or non-metallicsolid or flexible wall or pipe assembly or a liquid surface used as acollecting and coalescer medium for collecting droplets using theinterfacial tension adhesive property of liquids to be attracted to asurface. Depending on the liquid nature (wetting or non-wetting), thecollector surface may be conditioned to assure spreading of the“oil-wet” or “water-wet” collected droplets and the formation of smallpools, liquid films or rivulets through coalescence of collecteddroplets.

(b) Drainage Mechanism

The purpose of the drainage mechanism is to drain or remove thecollected droplets from the collector surface.

A liquid film comprising coalesced collected droplets may be directlyeliminated or drained to some other location, such as for disposal, ormay be received in a collection vessel, where the collected droplets mayundergo further separation using mechanical separation techniques orother separation techniques. The collection vessel may also be used tocontain the collected droplets in the event that the droplets are toxicor should otherwise be isolated from the surrounding atmosphere.

The method and apparatus must create flow conditions of the gas streamleading to a transitional or turbulent flow regime in the vicinity ofthe collector surface, since turbulence is the main mechanism used toproject droplets entrained in the gas stream toward the collectorsurface. The method and apparatus should preferably also minimizere-atomization and re-entrainment of collected droplets back into thegas stream through breaking of pools, films or rivulets of collecteddroplets.

As a result, the flow of the gas stream through the flowpath should bemanaged to provide a flow which is substantially turbulent but moderatein order to avoid re-atomization and re-entrainment of collecteddroplets. Such moderation can be achieved by controlling one or moreflow parameters relating to the flow of the gas stream through theflowpath. Such flow parameters may relate to a maximum Weber numberwithin the flowpath, to the maintenance of annular flow conditionswithin the flowpath, to the superficial gas velocity of the gas streamthrough the flowpath, or to some other parameter.

The actual design of an apparatus or method utilizing the inventionshould take into account some other factors; which may, for example, bedependent upon the material, configuration and other characteristics ofthe collector surface. The following are additional objectives which maybe considered in the design of an apparatus or method utilizing theinvention:

-   -   1. progressively reducing the flow area of the gas stream        axially along the flowpath in order to maintain the desired        turbulent flow regime.    -   2. providing the capability to divide the gas stream into        various flow elements or “sub-streams” for delivery to a        plurality of flowpaths, aiming at a proper balance between        flowrate, throughput, and maximum utilization of “collector        surface collection area”.

Having regard to the above general considerations, the preferredembodiments of the invention are directed at the following:

-   -   (a) the separation of liquid droplets (pure liquid or containing        gas or solids) carried by a gas stream, in conjunction with a        process involving gas cleaning, removal of solid particles, gas        washing or direct gas-liquid/gas-liquid-solid contact reactions        where the droplets are of relatively small dimensions;    -   (b) the separation of impure or pure droplets using the effect        of intrinsic flow turbulence (micro-turbulence) and a system        design to allow for creating a high probability of impacting the        droplets with large “collector surface” areas where collection        of the droplets on the collector surface is achieved due to        interfacial tension adhesion;    -   (c) using vertical or inclined collector surfaces in order to        create a favourable environment for coalescing and draining of a        large number of collected droplets facilitated by forming small        pools, liquid films or rivulets of coalesced collected droplets        on the collector surface;    -   (d) draining the collected droplets and all or a portion of the        gas stream through a drainage mechanism comprising a system of        slits and collectors and allowing the collected droplets and the        drained gas stream to move from a “high-turbulence gas droplets        area” within the flowpath to an external collection area        (collection vessel) which may provide for further separation        amongst gas, liquid and solid phases;    -   (e) designing the collector surface and the flow characteristics        of the gas stream to avoid excessive turbulence within the        flowpath, in order to minimize the re-atomization or        re-entrainment of droplets into the gas stream or in order to        maximize the size of droplets which do become re-atomized or        re-entrained in the gas stream; and    -   (f) designing the drainage mechanism to avoid excessive        turbulence within the drainage mechanism, in order to minimize        the re-atomization and re-entrainment of droplets into the gas        stream or in order to maximize the size of droplets which do        become re-atomized or re-entrained in the gas stream.

Referring to FIG. 1, there is depicted an apparatus according to a firstpreferred embodiment of the invention which is intended for use inprocessing relatively large quantities of gas at relatively low pressureand carrying liquid droplets with or without solid particles attached,and with or without suspensions of viscous (“gum”) materials asadditional impurities.

The apparatus of FIG. 1 is a planar collector surface apparatus (20) inwhich a flowpath (22) is defined by a collector surface (24) comprisinga plurality of substantially planar surfaces. The collector surface (24)is preferably constructed of metal plates or sheets and is preferablytextured to promote turbulent flow within the flowpath (22). Thetexturing may be comprised of corrugations, waves, ribs or a rougheningof the collector surface (24). As depicted in FIG. 1, the collectorsurface (24) includes texturing comprising corrugations or waves. Thecollector surface (24) is preferably treated to resist corrosion anderosion and is also treated to be “wettable” by the liquid dropletswhich are intended to be removed from the gas stream.

As depicted in FIG. 1, the collector surface (24) is further comprisedof additional surfaces (26) contained within the flowpath (22). Theadditional surfaces (26) each comprise substantially planar surfaces andfunction as additional collector surfaces for collecting liquiddroplets. The additional surfaces (26) divide the flowpath (22) into aplurality of sub-flowpaths (28). The planar collector surface apparatus(20) may alternatively include a plurality of flowpaths instead of asingle flowpath (22) having a plurality of sub-flowpaths (28).

The planar collector surface apparatus (20) is further comprised of aflow conditioner (30) for conditioning the gas stream and a distributor(31) for distributing the gas stream amongst the sub-flowpaths (28). Asdepicted in FIG. 1, the flow conditioner (30) and the distributor (31)are provided by a combined conditioner/distributor (35). Alternatively,the distributor (31) may be separate from the flow conditioner (30).

The combined conditioner/distributor (35) is connected with a source(not shown) for the gas stream, which source delivers the gas stream tothe combined conditioner/distributor (35) as a flowing gas stream.Alternatively, the flow conditioner (30) or the combinedconditioner/distributor (35) may be further comprised of a device, suchas a pump (not shown) or a fan (not shown), for imparting flow to thegas stream.

As depicted in FIG. 1, the combined conditioner/distributor (35) iscomprised of an admission chamber (32), which has a conical shape forprogressively increasing the velocity of the gas stream to a level whichwill provide substantially turbulent flow of the gas stream. Thecombined conditioner/distributor (35) is further comprised of a grid(34) for imparting pseudo-homogeneous turbulent flow conditions to thegas stream after it has exited the admission chamber (32) by eliminatingor minimizing large turbulent vortexes which may have resulted fromducts or elbows upstream of the admission chamber (32).

The flowpath (22), including the sub-flowpaths (28), and the collectorsurface (24) are completely contained within a closed collection vessel(36). The collection vessel (36) defines a gas inlet (38), a liquiddrainage outlet (40), and a gas outlet (42). The combinedconditioner/distributor (35) is positioned adjacent to the gas inlet(38).

The flowpath (22) is contained entirely within the collection vessel(36). The flowpath (22) is comprised of a flowpath inlet (39) and aflowpath end (43). The flowpath inlet (39) is connected to the combinedconditioner/distributor (35) so that the gas stream from the source isdivided into separate gas streams for each of the sub-flowpaths (28).The flowpath (22) terminates at the flowpath end (43).

The flowpath (22) includes a first section (44) and a second section(45). As depicted in FIG. 1, the first section (44) of the flowpath (22)is comprised of three sub-flowpaths (28), while the second section (45)of the flowpath (22) is comprised of two sub-flowpaths (28).

The planar collection surface apparatus (20) is further comprised of adrainage mechanism (46) for draining coalesced collected droplets whichare collected on the collector surface (24), and for draining the gasstream from the flowpath (22). The drainage mechanism (46) is comprisedof a plurality of slits (48) which are defined by the collector surface(24). The sections (44,45) of the flowpath (22) are declined andinclined respectively to encourage movement of the coalesced liquiddroplets toward the slits (48) and to encourage further coalescence ofcollected droplets.

The slits (48) are spaced axially between the flowpath inlet (39) andthe flowpath end (43). The sections (44,45) of the flowpath (22) aresized, and the slits (48) are spaced and sized so that an amount of thegas stream passes through the slits (48) with the collected liquiddroplets at substantially the same velocity through each of the slits(48). In addition, the velocity of the gas stream through each of theslits (48) is preferably controlled to minimize re-atomization orre-entrainment of liquid droplets or to maximize the size of anydroplets which do re-atomize or re-entrain in the gas stream.

The drainage mechanism (46) may be further comprised of troughs orgrooves (not shown) in the collector surface (24) for directingcollected liquid droplets toward the slits (48).

The planar collector surface apparatus (20) is further comprised of awasher (52) for washing the apparatus (20) to remove residue and otherimpurities therefrom. The washer (52) is preferably comprised of aspraying system by which water or some other solvent can be sprayed ontothe collector surface (24).

The planar collector surface apparatus (20) is also further comprised ofa cooler (54) positioned within the combined conditioner/distributor(35) for cooling the gas stream before the gas stream enters theflowpath (22).

In operation, a gas stream from the source is passed through the cooler(54) in order to condense water vapor contained in the gas stream and/orincrease the size of liquid droplets contained in the gas stream. Fromthe cooler (54), the gas stream is passed through the combinedconditioner/distributor (35) where the gas stream is conditioned,divided and distributed substantially evenly to the sub-flowpaths (28)under substantially turbulent conditions such that the probability ofliquid droplets contacting the collector surface (24) can be enhancedwhile the re-entrainment of the liquid droplets into the gas stream canbe minimized.

The liquid droplets contained in the gas stream pass through thesub-flowpaths (28) generally axially, contact or nearly contact thecollector surface (24) due to the turbulent flow conditions and becomecollected on the collector surface (24) due to adhesion forces betweenthe liquid droplets and the collector surface (24). The collected liquiddroplets coalesce together and form a liquid film of coalesced collecteddroplets on the collector surface (24) which film is drained in acontrolled manner from the collector surface (24) through the slits (48)in the collector surface (24), along with the gas stream.

The drained collected droplets and the drained gas stream are receivedin the collection vessel (36), where they may undergo further secondaryseparation to separate liquid from the gas phase of the gas stream or toseparate solid particles from either the liquid or the gas phase. Fromthe collection vessel (30), the various separated products mayoptionally be directed to additional separation apparatus (not shown) toprovide for multi-stage separation.

The product gas stream exits the collection vessel through the gasoutlet (42). The product gas stream may then be stored, disposed of, ordelivered for use in an apparatus such as a compressor, turbine, orburner, depending upon the composition of the gas stream and theparticular application of the invention.

The operation of the planar collector surface apparatus (20) may beinterrupted intermittently so that that the apparatus (20) can becleaned and restored using the washer (52).

Referring to FIG. 2, there is depicted an apparatus according to asecond preferred embodiment of the invention, which may be suitable forprocessing relatively small quantities of gas, but potentially at arelatively high pressure, with or without solid particles attached, andwith or without suspensions of viscous (“gum”) materials as additionalimpurities.

The apparatus of FIG. 2 is a cylindrical collector surface apparatus(120) in which a first flowpath (122) is defined by a first collectorsurface (124) comprising a conduit or pipe. The first collector surface(124) is preferably constructed of cylindrical metal tubing and ispreferably textured to promote turbulent flow within the first flowpath(122). The first collector surface (24) is preferably treated to resistcorrosion and erosion and is also treated to be “wettable” by the liquiddroplets which are intended to be removed from the gas stream.

As depicted in FIG. 2, the cylindrical collector surface apparatus (120)is further comprised of a second flowpath (126) which is defined by asecond collector surface (128) comprising a conduit or pipe. The secondcollector surface (128) is preferably similar to the first collectorsurface (124) with respect to materials and construction. Although thesecond flowpath (126) is depicted in FIG. 2 as being the same size asthe first flowpath (122), the second flowpath (126) could be smaller orlarger than the first flowpath (122). The cylindrical collector surfaceapparatus (120) may alternatively include a single flowpath or more thantwo flowpaths.

Referring to FIGS. 2-3, the cylindrical collector surface apparatus(120) is further comprised of a flow conditioner (130) for conditioningthe gas stream and a distributor (131) for distributing the gas streamto the flowpaths (122,126). As depicted in FIG. 2, the flow conditioner(130) and the distributor (131) are provided by a combinedconditioner/distributor (135). Alternatively, the distributor (131) maybe separate from the flow conditioner (30).

The combined conditioner/distributor (135) is connected with a source(not shown) for the gas stream, which source delivers the gas stream tothe combined conditioner/distributor (135) as a flowing gas stream.Alternatively, the flow conditioner (130) or the combinedconditioner/distributor (135) may be further comprised of a device, suchas a pump (not shown) or a fan (not shown), for imparting flow to thegas stream.

As depicted in FIGS. 2-3, the combined conditioner/distributor (135) iscomprised of a distributor manifold (132) which includes a turbulencepromoting orifice (134) for each of the flowpaths (122,126). Thedistributor manifold (132) distributes the gas stream to the flowpaths(122,126) and the turbulence promoting orifices (134) condition the gasstream to provide substantially turbulent flow of the gas stream througheach of the flowpaths (122,126).

The flowpaths (122,126) and the collector surfaces (124,128) arecompletely contained within a closed collection vessel (136). Thecollection vessel (136) defines a gas inlet (138) adjacent to a firstend (140) of the collection vessel (136), a liquid drainage outlet(141), and a gas outlet (142) between the first end (140) and a secondend (144) of the collection vessel (136). The combinedconditioner/distributor (135) is positioned within the collection vessel(136) adjacent to the gas inlet (138).

Each of the flowpaths (122,126) is comprised of a flowpath inlet (139)and a flowpath end (143). The flowpaths (122,126) terminate at theflowpath ends (143). The flowpath inlets (139) for each of the flowpaths(122,126) are connected to the combined conditioner/distributor (135) sothat the gas stream from the source is divided into separate gas streamsfor each of the flowpaths (122,126).

The cylindrical collection surface apparatus (120) is further comprisedof a drainage mechanism (146) for draining coalesced collected dropletswhich are collected on the collector surfaces (124,128), and fordraining the gas stream from the flowpaths (122,126). The drainagemechanism (146) is comprised of a plurality of slits (148) which aredefined by the collector surfaces (124,128). The flowpaths (124,128) arepartly declined and partly inclined to encourage movement of thecoalesced collected droplets toward the slits (148) and to encouragefurther coalescence of collected droplets.

The slits (148) are oriented transversely in the collector surfaces(124,128), are spaced axially between the flowpath inlets (139) and theflowpath ends (143). The slits (148) are spaced and sized so that anamount of the gas stream passes through the slits (148) with thecollected liquid droplets at substantially the same velocity througheach of the slits (148). In addition, the velocity of the gas streamthrough each of the slits (148) is preferably controlled to minimizere-atomization or re-entrainment of liquid droplets or to maximize thesize of any droplets which do re-atomize or re-entrain in the gasstream.

The drainage mechanism (135) may be further comprised of troughs orgrooves (not shown) in the collector surfaces (124,128) for directingcollected liquid droplets toward the slits (148).

The cylindrical collector surface apparatus (120) is further comprisedof a cooler (154) positioned upstream of the combinedconditioner/distributor (135) for cooling the gas stream before the gasstream enters the flowpaths (122,126).

In operation, a gas stream from the source is passed through the cooler(154) in order to condense water vapor contained in the gas streamand/or increase the size of liquid droplets contained in the gas stream.From the cooler (154), the gas stream is passed through the combinedconditioner/distributor (135) where the gas stream is conditioned,divided and distributed substantially evenly to the flowpaths (122,126)under substantially turbulent conditions such that the probability ofliquid droplets contacting the collector surfaces (124,128) can beenhanced while the re-entrainment of the liquid droplets into the gasstream can be minimized.

The liquid droplets contained in the gas stream pass through theflowpaths (122,126) generally axially, contact the collector surfaces(124,128) due to the turbulent flow conditions and become collected onthe collector surfaces (124,128) due to adhesion forces between theliquid droplets and the collector surfaces (124,128). The collectedliquid droplets coalesce together and form a liquid film of coalescedcollected droplets on the collector surfaces (124,128) which is drainedin a controlled manner from the collector surfaces (124,128) through theslits (148), along with the gas stream.

The drained collected droplets and the drained gas stream are receivedin the collection vessel (136), where they may undergo further secondaryseparation to separate liquid from the gas phase of the gas stream or toseparate solid particles from either the liquid or the gas phase. Fromthe collection vessel (130), the various separated products mayoptionally be directed to additional separation apparatus (not shown) toprovide for multi-stage separation.

The product gas stream exits the collection vessel through the gasoutlet (142). The product gas stream may then be stored, disposed of, ordelivered for use in an apparatus such as a compressor, turbine, orburner, depending upon the composition of the gas stream and theparticular application of the invention.

1. An apparatus for removing liquid droplets from a gas stream, theapparatus comprising: (a) a flowpath for the gas stream, the flowpathcomprising a flowpath inlet; (b) a collector surface, positionedadjacent to the flowpath so that the gas stream is in communication withthe collector surface as the gas stream passes through the flowpath, forcollecting the droplets as collected droplets; (c) a flow conditioner incommunication with the flowpath inlet, for conditioning the gas streamto provide substantially turbulent and generally axial flow of the gasstream through the flowpath; and (d) a drainage mechanism associatedwith the collector surface, for draining the collected droplets from thecollector surface.
 2. The apparatus as claimed in claim 1 wherein theflowpath is defined by the collector surface.
 3. The apparatus asclaimed in claim 1 wherein the collector surface is comprised of agenerally planar surface.
 4. The apparatus as claimed in claim 2 whereinthe collector surface is comprised of a plurality of generally planarsurfaces.
 5. The apparatus as claimed in claim 2 wherein the collectorsurface is comprised of a generally cylindrical surface.
 6. Theapparatus as claimed in claim 2 wherein the drainage mechanism iscomprised of at least one aperture defined by the collector surface. 7.The apparatus as claimed in claim 2 wherein the drainage mechanism iscomprised of a plurality of slits defined by the collector surface. 8.The apparatus as claimed in claim 7 wherein the flowpath is furthercomprised of a flowpath end and wherein the slits are spaced axiallyalong the collector surface between the flowpath inlet and the flowpathend.
 9. The apparatus as claimed in claim 2 wherein the flowpath isfurther comprised of a flowpath end and wherein the flowpath is orientedso that the flowpath end is positioned below the flowpath inlet.
 10. Theapparatus (as claimed in claim 2, further comprising a collection vesselassociated with the drainage mechanism, for receiving the drainedcollected droplets.
 11. The apparatus as claimed in claim 2 wherein theflowpath is further comprised of a flowpath end and wherein the drainagemechanism drains the gas stream from the flowpath, further comprising acollection vessel associated with the drainage mechanism, for receivingthe drained collected droplets and the drained gas stream.
 12. Theapparatus as claimed in claim 11 wherein the collection vessel iscomprised of a gravity separation vessel, for separating the drainedcollected droplets and the drained gas stream into a plurality ofproducts.
 13. The apparatus as claimed in claim 2 wherein the collectorsurface is wettable by the droplets.
 14. The apparatus as claimed inclaim 2 wherein the collector surface is a textured surface.
 15. Theapparatus as claimed in claim 5 wherein the flowpath has a diameter ofbetween about 15 millimeters and about 50 millimeters.
 16. The apparatusas claimed in claim 2, further comprising a cooler for cooling the gasstream before the gas stream enters the flowpath.
 17. An apparatus forremoving liquid droplets from a gas stream, the apparatus comprising:(a) a plurality of parallel flowpath assemblies, each of the flowpathassemblies comprising: (i) a flowpath for the gas stream, the flowpathcomprising a flowpath inlet; (ii) a collector surface, positionedadjacent to the flowpath so that the gas stream is in communication withthe collector surface as the gas stream passes through the flowpath, forcollecting the droplets as collected droplets; (iii) a flow conditionerin communication with the flowpath inlet, for conditioning the gasstream to provide substantially turbulent and generally axial flow ofthe gas stream through the flowpath; (iv) a drainage mechanismassociated with the collector surface, for draining the collecteddroplets from the collector surface; and (b) a distributor associatedwith the flowpath inlets, for distributing the gas stream to theflowpaths.
 18. The apparatus as claimed in claim 17 wherein each of theflowpaths is defined by the collector surfaces.
 19. The apparatus asclaimed in claim 18 wherein each of the collector surfaces is comprisedof generally planar surfaces.
 20. The apparatus as claimed in claim 18wherein each of the collector surfaces is comprised of generallycylindrical surfaces.
 21. The apparatus as claimed in claim 18 whereineach of the drainage mechanisms is comprised of a plurality of aperturesdefined by the collector surface.
 22. The apparatus as claimed in claim18 wherein each of the drainage mechanisms is comprised of a pluralityof slits defined by the collector surface.
 23. The apparatus as claimedin claim 22 wherein each of the flowpaths is further comprised of aflowpath end and wherein the slits are spaced axially along thecollector surface between the flowpath inlet and the flowpath end. 24.The apparatus as claimed in claim 18 wherein each of the flowpaths isfurther comprised of a flowpath end and wherein each of the flowpaths isoriented so that the flowpath end is positioned below the flowpathinlet.
 25. The apparatus as claimed in claim 18, further comprising acollection vessel associated with the drainage mechanisms, for receivingthe drained collected droplets.
 26. The apparatus as claimed in claim 18wherein each of the flowpaths is further comprised of a flowpath end andwherein the drainage mechanisms drain the gas stream from the flowpath,further comprising a collection vessel associated with the drainagemechanisms, for receiving the drained collected droplets and the drainedgas stream.
 27. The apparatus as claimed in claim 26 wherein thecollection vessel is comprised of a gravity separation vessel, forseparating the drained collected droplets and the drained gas streaminto a plurality of products.
 28. The apparatus as claimed in claim 18wherein each of the collector surfaces is wettable by the droplets. 29.The apparatus as claimed in claim 18 wherein each of the collectorsurfaces is a textured surface.
 30. The apparatus as claimed in claim 20wherein each of the flowpaths has a diameter of between about 15millimeters and about 50 millimeters.
 31. The apparatus as claimed inclaim 18, further comprising a cooler associated with each of theflowpath inlets, for cooling the gas stream before the gas stream entersthe flowpaths.
 32. A method of removing liquid droplets from a gasstream, comprising: (a) conditioning the gas stream so that the gasstream exhibits substantially turbulent flow; (b) passing the gas streamgenerally axially through a flowpath under substantially turbulent flowconditions so that the gas stream is in communication with a collectorsurface positioned adjacent to the flowpath, thereby causing thedroplets to collect on the collector surface as collected droplets; and(c) draining the collector surface to remove the collected droplets fromthe collector surface.
 33. The method as claimed in claim 32 wherein thegas stream is passed through the flowpath such that re-entrainment intothe gas stream of the collected droplets is minimized.
 34. The method asclaimed 32 wherein the gas stream is passed through the flowpath at asuperficial velocity which is less than the critical atomization gasvelocity of the gas stream in the flowpath.
 35. The method as claimed inclaim 32 wherein the gas stream is passed through the flowpath underconditions such that the Weber number is less than or equal to about 30.36. The method as claimed in claim 32 wherein the flowpath is generallycylindrical and wherein the gas stream is passed through the flowpathsubstantially under annular flow conditions.
 37. The method as claimedin claim 32 wherein the gas stream is passed through the flowpath at asuperficial velocity of no greater than about 10 meters per second. 38.The method as claimed in claim 32 wherein the gas stream is passedthrough the flowpath at a superficial velocity of no greater than about8 meters per second.
 39. The method as claimed in claim 32 wherein thegas stream is passed through the flowpath at a superficial velocity ofbetween about 6 meters per second and about 8 meters per second.
 40. Themethod as claimed in claim 32 wherein the flowpath is generallycylindrical and wherein the flowpath has a diameter of between about 15millimeters and about 50 millimeters.
 41. The method as claimed in claim32 wherein the flowpath is comprised of a flowpath inlet and a flowpathend and wherein the flowpath is oriented so that the flowpath end isbelow the flowpath inlet.
 42. The method as claimed in claim 41 whereinthe draining step is comprised of allowing the collected droplets tomove along the collector surface under the influence of gravity.
 43. Themethod as claimed in claim 32 wherein the collector surface defines atleast one aperture and wherein the draining step is further comprised ofallowing an amount of the collected droplets to pass through theaperture.
 44. The method as claimed in claim 32, further comprising thestep of receiving in a collection vessel the collected droplets whichare drained from the collector surface.
 45. The method as claimed inclaim 32 wherein the draining step is further comprised of draining thegas stream from the flowpath with the collected droplets.
 46. The methodas claimed in claim 45, further comprising the step of receiving in acollection vessel the drained collected droplets and the drained gasstream.
 47. The method as claimed in claim 46, further comprising thestep, following the collection vessel receiving step, of separating thedrained collected droplets and the drained gas stream to produce aplurality of products.
 48. The method as claimed in claim 32, furthercomprising the step, before the step of passing the gas stream throughthe flowpath, of cooling the gas stream.
 49. The method as claimed inclaim 32 wherein at least fifty percent of the droplets by weight have asize within a range of sizes between about 1 μm and about 100 μm. 50.The method as claimed in claim 32 wherein at least fifty percent of thedroplets by weight have a size within a range of sizes between about 1μm and about 50 μm.
 51. The method as claimed in claim 32 wherein atleast fifty percent of the droplets by weight have a size within a rangeof sizes between about 1 μm and about 20 μm.
 52. The method as claimedin claim 32 wherein the collector surface is wettable by the droplets.53. The method as claimed in claim 32, further comprising the step ofcoalescing the collected droplets on the collector surface beforedraining the collected droplets.